Integrated delivery system for chemical vapor from non-gaseous sources for semiconductor processing

ABSTRACT

An integrated module with a heated reservoir to vaporize liquid for semiconductor processes with liquid sources is presented. Shut-off valves and a proportioning pressure valve for controlling the flow of the vapor from the reservoir are mounted on the module for simple conduction heating of the valves. A capacitance manometer also mounted to the module also has its own heating elements. Condensation of the vapor is avoided and consistence performance and reliability is obtained.

This application is a continuation of Ser. No. 708,421, filed May 31,1991, now U.S. Pat. No. 5,252,134.

BACKGROUND OF THE INVENTION

The present invention relates to semiconductor wafer processingequipment and, more particularly, to delivery systems for chemicalvapors from liquid sources.

In the processing of semiconductor wafers, many processes require thedelivery of gases into a processing chamber in which one or moresemiconductor wafers are placed. Typically these gases at their sourcesare in the form of gases, such as nitrogen, oxygen, hydrogen, arsine,etc., in pressurized tanks. However, some processes use gases which areliquid at their sources. The liquid is heated to a vapor which isintroduced into the processing chamber.

To create a chemical vapor from liquid sources, delivery systems forliquid sources heretofore have used a bubbler unit or a heatedreservoir. In a bubbler unit a inert gas, such as nitrogen, is bubbledthrough the liquid source to carry the molecules of the chemical alongwith the inert gas. In heated reservoirs the liquid is heated tovaporize the source chemical for delivery.

In these systems other discrete units, such as valves, pressure and massflow controllers, and the feedline through which the chemical vaporpasses, are connected between the bubbler or reservoir unit and theprocessing chamber. Each of the discrete units may be heated. In anycase, problems arise with these complicated delivery systems.Condensation forms at the unheated or inadequately heated points of thesystem. Reliability is poor and the consistency of performance isproblematical.

Furthermore, the mass flow controllers of these systems have limitedperformance. These mass flow controllers are difficult to operate attemperatures above 70° C. because they use a heated bypass sensor tosense flow. This sensor has two sections. The first section has(electrical) resistance-heated walls to heat the gas. The second sectionis unheated and measures the temperature of heated gas from the firstsection. The difference in temperature of the gas entering the bypassand the gas leaving the bypass is measured to determine the rate of thegas flow. At gas temperatures of 70° C. and above, the difference intemperatures becomes so small that the rate of gas flow is difficult forthese present day mass flow controllers to determine. Additionally, thesecond unheated section is a source of condensation problems.

The present invention solves or substantially mitigates many of theseproblems of delivering a chemical vapor to a processing chamber from aliquid source. The present invention is integrated and the problems ofcomplexity of present day systems are avoided. Consistency ofperformance and reliability are greatly improved over present daysystems. Furthermore, the present invention is adaptable to even solidsources.

SUMMARY OF THE INVENTION

The present invention provides for an integrated chemical vapor deliverysystem from a liquid source to a processing unit with a processingchamber therein for semiconductor wafers. The system has a housing withconnections so that the housing can be mounted to the processing unit. Areservoir in the housing is connected to the source and to theprocessing chamber when the module housing is mounted to said processingunit. The reservoir holds the liquid from the source. The reservoir inthe housing is heated by heating elements so that liquid in thereservoir is transformed into a vapor. A valve in the vapor flow fromsaid reservoir to said processing chamber controls the delivery of thevapor.

Sensors for properties of the vapor flow from the reservoir to theprocessing chamber, such as pressure in the processing chamber or massflow of the vapor from the reservoir to the processing chamber, providea feedback control path for control of the vapor delivery.

The present invention also provides for a system for delivering chemicalvapor effectively and efficiently from a liquid source for theprocessing of semiconductor wafers. The system has a processing unit anda vapor supply module. The processing unit has a housing defining aprocessing chamber for semiconductor wafers, a gas inlet, gas supplychannels connected to the gas inlet for supplying gas to said processingchamber, and vacuum channels for removing gas from said processingchamber.

BRIEF DESCRIPTION OF THE DRAWINGS

A clear understanding of the present invention may be achieved byperusing the following detailed Description of Specific Embodiments withreference to the following drawings:

FIG. 1 is an overall schematic view of a chemical vapor delivery systemaccording to the present invention.

FIG. 2A is a cross-sectional side view of the integrated chemical vapordelivery module according to the present invention;

FIG. 2B is another cross-sectional side view of the module of FIG. 2A.

FIG. 3A is a schematic side view of the capacitance manometer and itsfitting mounted to the module of FIG. 2A and 2B;

FIG. 3B is a bottom view of the manometer of FIG. 3A; and

FIG. 3C is a flattened view of the heating elements for the manometer ofFIG. 3A.

FIG. 4 is a side view of the processing chamber of the chemical vapordelivery system of FIG. 1.

FIG. 5 illustrates a top view of the gas supply channels for theprocessing chamber of FIG. 2.

FIG. 6 illustrates in a vertical view how the module mounts to theprocessing unit in the chemical vapor delivery system of FIG. 1.

FIG. 7 schematically illustrates a modification of the module with threegas channels according to the present invention.

FIG. 8 schematically illustrates a modification of the module with a gasflow sensor according to the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

FIG. 1 is an overall schematic illustration of a semiconductorprocessing system with one embodiment of a chemical vapor deliverysystem according to the present invention. In the FIG. 1 system, thechemical delivered is a silylation agent.

Silylation agents are one class of liquid sources in semiconductorprocessing. These agents are beginning to be used in advancedsemiconductor processes requiring very high resolution. In semiconductorprocessing, after a layer of photoresist has been deposited on asemiconductor wafer and has been exposed to a pattern of light, thephotoresist must be developed. With a silylation process in photoresistdeveloping, the photoresist layer need only be exposed at the very topof the layer. This permits photolithography with light at shortwavelengths and large numerical apertures without a large depth offocus. High resolution of features "imprinted" upon the semiconductorwafer during processing is ensured.

For silylation the agents must be heated and the resulting vaporsupplied to the processing chamber at precise pressures andtemperatures. As explained above, present day delivery systems forsilylating agents are formed by a reservoir connected to a liquid sourceof the agents. The reservoir is heated and the vapor fed into theprocessing chamber by a feed line.

These systems are very difficult to maintain during operation. To avoidcondensation of an agent, the feedline must be heated along with thevarious fittings between the process chamber and the reservoir.Nonetheless condensation remains a constant problem. Furthermore, theuneven heating at various points of the system leads to difficulties indelivering the silylating agent vapor to the processing chamber atprecise temperatures and pressures.

To solve these problems for silylation agents, the FIG. 1 deliverysystem has an integrated chemical delivery module 11 which is attachedto a processing unit 10 containing a processing chamber in which asemiconductor wafer is placed during processing. The module 11 supplieschemical vapor into the processing chamber from a supply 12 of chemicalsin liquid form.

A vacuum pump 14 removes gas from the processing chamber through valves23 and 24, which maintain a vacuum in the processing chamber. The vacuumpump 14 is also connected to an effluent handling unit (not shown) andan oil filtration system unit 15 for removing contaminants from the pumpoil.

The nitrogen source 13 also supplies nitrogen for the processing chamberthrough a valve 25 and a flow meter 27. The valve 25 helps in thebackfill of the processing chamber with N₂ when the processing chamberis raised from a vacuum to atmospheric pressure. The nitrogen source 13is also connected to the pump 14 through a valve 26. The nitrogen to thepump 14 purges the pump oil to reduce the absorption of contaminants,such as silylating agents, into the oil. Finally the nitrogen source 13is connected to the liquid source 12 to pressurize the source 12 tosupply liquid to the module 11. A check valve 28 prevents backing of theliquid to the nitrogen source 13.

To monitor the pressure within the processing chamber, a capacitancemanometer 18 is attached to the processing unit 10 and coupled to theprocessing chamber. The manometer 18 is coupled to an electronic controlunit 17 which is connected to a proportioning pressure valve 21 in themodule 11.

The module 11 has a reservoir which receives the chemical liquid fromthe liquid supply 12 through a liquid refill valve 22, a shut-off valve,which is integrally mounted to module 11. The reservoir is heated tochange the liquid into a chemical vapor which then passes through achamber feed valve 20, a shut-off valve, and the proportioning pressurevalve 21. The two valves 21 and 22 are also integrally mounted to themodule 11. Responsive to the signals from the unit 17, the valve 21controls the pressure in the processing chamber by supplying more orless chemical vapor to the chamber. The module 11 also has a capacitancemanometer 19 for accurately monitoring the pressure of the chemicalvapor within the reservoir.

FIGS. 2A and 2B show the details of the structure of the module 11 moreclearly. As shown in FIG. 2A, the module 11 has an upper housing unit41A and a lower housing unit 41B, both of which are made from stainlesssteel. For operation, the units 41A and 41B are clamped together bybolts 45 shown in FIG. 2B.

In the lower housing unit 41B there is the liquid reservoir 44 outlinedby a dotted line. Connected to the reservoir 44 is a vacuum fitting 52mounted to the lower housing 41B. As an aside, it should be noted thatall fittings are vacuum-tight to prevent leakage of liquid or vapor. Thefitting 52 is connected to the liquid refill valve 22, Model4V1P4K11ACSS, manufactured by Parker Hannafin of Huntsville, Ala., whichis connected to the liquid source 12 by a refill line. The valve 22 isintegral with the module 11 and forms a liquid supply channel with thefitting 52 and the refill line.

Mounted to the top housing 41A is the proportioning pressure valve 21,the chamber feed valve 20, the capacitance manometer 19, and the liquidlevel sensor 43. The sensor 43 is mounted to the housing 41A by athreaded (NPT) fitting 53. The sensor 43, Model 511S, manufactured byGenelco of Port Huron, Mich., determines the level of the liquid in thereservoir 44 so that the valve 22 can keep the reservoir 44 filled withliquid.

The manometer 19, Model 622B from Edwards High Vacuum of Wilmington,Mass., is attached to the housing unit 41A by a fitting 59, Model 8BVSSfrom Parker Hannafin of Huntsville, Ala., mounted to the unit 41A. Thecapacitance manometer 19 accurately measures the pressure of thevaporized liquid from the reservoir 44 as a check on the pressure.

The proportioning pressure valve 21, manufactured by PFD of San Jose,Calif., is a custom model with chemical resistant seals and a hightemperature operating coil. The valve 21 is mounted to the housing 41Aby a fitting 61 so that the valve 21 controls the passage of the vaporfrom the reservoir 44. The fitting 61 is also connected to a fitting 60which is also mounted to the housing 41A. The fitting 60 holds thechamber feed valve 21, Model KIT2173 from Parker Hannafin, so that thepassage of the vapor from the reservoir 44 can be turned off and on. Thefitting 61 has an outlet 62 is directly connected to a gas inlet to theprocessing chamber of the processing unit 10 when the module 11 ismounted to the unit 10. The fittings 61 and 60 form a gas channel fromthe reservoir 44 to the inlet of the processing chamber.

Also mounted lengthwise in the top housing 41A are two resistance rodheaters 42, shown in cross-section in FIG. 2B. The rod heaters,manufactured by W. W. Grainger of Chicago, Ill., are inserted inone-quarter inch diameter holes drilled lengthwise in the housing 41A.With an electric current, the heaters 42 heat the units 41A and 41B andthe liquid in the reservoir 44.

For additional heating to augment the thermal energy from the rods 42,piezoelectric transducers may also be mounted to the housing 41A, 41B.The sonic energy from the transducers, operating in a range of600-1800KHz, provide another source of heating to the reservoir 44 andthe liquid and vapor in and from the reservoir 44.

Because the valves 20, 21, which are intimately seated in the housing41, and the manometer 19 mounted directly to the housing 41A, they areheated by conduction. This arrangement avoids heat sinks which may causethe undesirable condensation of the heated vapor from the reservoir 44.Furthermore, the manometer 19, and the manometer 18, are also designedso that they are efficiently heated. Typically these manometers have ashaft separating the sensing area of the manometer and its fitting. Inthe present invention the shaft eliminated so that the sensing area ofthe manometer 19 is directly connected to the fitting 59 as shown inFIG. 3A and 3B. Two heating elements, one element 64A wrapped around thesensing area (shaded in FIG. 3A) of the cylindrically-shaped manometer19 and the other element 64B attached to circularly-shaped sensing area63 around the fitting 59 (seen in the bottom view of the manometer inFIG. 3B), heat the manometer 19. These heating elements are formed fromheating foils embedded in silicon rubber insulation material. They areshaped as shown in FIG. 3C but are flexible so that the element 62A maybe wrapped around the cover of the manometers 19 and 18. Such heatingelements are manufactured by Watlow Electric of St. Louis, Miss.

As in many present day semiconductor processing equipment, the controlunit 17 of FIG. 1 has a microprocessor, a 80386sx from Intel corporationof Santa Clara, Calif., which controls the functions of the module 11 bywell-known programming techniques. Furthermore, not all the electricalconnections from the valves and sensors are shown in the drawings.

From the feedback signals of the manometer 18, the microprocessorcontrols the proportioning pressure valve 20 (and its heating) tomaintain the processing chamber 39 at the desired pressure. Themicroprocessor also controls the temperature of the reservoir 44 throughthe heating rods 42 to maintain the vapor in the module 11 at a desiredtemperature and pressure, and controls the liquid resupply of thereservoir 44 through the refill valve 22 under the feedback controlsignals from the liquid level sensor 43. It should be noted that thecontrol unit 17 can be connected to other sensors, as described below,to control the vapor flow from the module 11 into a processing chamber.

FIG. 4 is a cross-sectional side view of a processing chamber 39 in theprocessing unit 10 of FIG. 1. The processing chamber 39 is generallyshaped and sized to hold one semiconductor wafer 35. The chamber 39 isformed by a top housing plate 31A and bottom housing plate 31B.Typically these plates 31A and 31B are formed from stainless steel.

The processing chamber 39 is defined between the two housing plates 31Aand 31B when clamped together. In the region where a semiconductor waferis mounted for processing, the processing chamber has a height of 1 to 2inches. The length (and width) of the chamber 39 is approximately 11inches for 8-inch wafers, i.e., wafers having a 200 mm. diameter. Hencethe total volume of the chamber 39 is small, approximately 5 to 10 cubicinches. A rubber bushing 38 around the upper edge of the lower housingplate 31b ensures that the processing chamber 39 is sealed when theplates 31A and 31B are clamped together during operation.

The top housing plate 31A has several gas channels 36 which are part ofa vacuum chuck for the wafer in the processing chamber 39. The channels36 are connected to a vacuum source to hold the wafer firmly in placefor heat transfer during operation. A heater unit 32A is also mounted tothe top of the housing 31A. This unit 32A is formed by resistanceheating coils.

The bottom housing 31B has gas supply channels 33 which are allinterconnected to a gas inlet 40 by a supply channel 51. The channels 33form a circular pattern around a center axis 50 as explained below.Mounted to the bottom of the housing plate 31B is another heater unit32B formed by resistance heating coils.

It is very important that any reactant gas be supplied uniformly to asemiconductor wafer during processing. Viewed from above as shown inFIG. 5, the open gas supply channels 33 are radially distributed in thelower housing plate 31B around the center axis 50. The channels 33 havefour radial channels 33A from the center axis 50 which intersect evenlyspaced circular channels 33B centered about the axis 50. Duringoperation of the processing unit 10, the supplied vapor enters the gasinlet 40 from the outlet 62 of the module 11. Through the supply channel51 the vapor enters the radial channels 33A from the center axis 50 andis distributed to the circular channels 33B.

For vaporized silylating agents, channels of cross-sections ofapproximately 0.25 inches deep×0.40 inches wide for the radial channels33A, and radial spacing of 1.0 inches for the circular channels 33B workvery well in distributing the vapor.

Between the gas supply channels 33 and the chamber 39 there are twocircular plates 34A and 34B which fit into a circular slot 51 over theopen channels 33. In FIG. 4 the two plates 34A and 34B are shown as asingle plate 34. The plates 34A and 34B perform a gas dispersionfunction. The plate 34A, which is placed directly over the channels 33,has numerous holes of 0.030 inch diameter drilled in a pattern favoringthe outside, i.e., away from the center axis 50. In this manner the sameamount of gas is delivered to a unit volume of the processing chamber39. Typically, this plate is formed from stainless steel.

Above the first gas distribution plate 34A is the second gas dispersionplate 34B. The plate 34B disperses the gases from the channels 33 morefinely than the plate 34A. The plate 34B is formed from pressed metal,stainless steel or porous graphite and has no visible holes. Nonethelessgas can pass through the plate 34B. Thus the incoming gas vapor from thechannels 33 are distributed by the plate 34A and leak through thedispersion plate 34B into the processing chamber 39.

To hold a semiconductor wafer 35 in place in the chamber, a wafer holder37 is used. During processing, the wafer 35A is placed facedown towardthe gas distribution channels 33. Once the top housing plate 31A isclosed, the wafer is held in place and in contact with the plate 31A bythe vacuum channels 36.

FIG. 6 is a top view of the processing chamber 39 with a wafer 35 andillustrates schematically how a module 11 is connected to the processingunit 10. The housing of the module 11 is bolted to the housing of theprocessing unit 10 so that the outlet 62 is connected tightly to the gasinlet 40 to the processing chamber.

The manometer 18 monitors the pressure in the processing chamber 39 witha wafer 35, an exhaust valve 23 removes the vapors from the chamber 39,and a valve 25 controls the nitrogen flow from the nitrogen supply 13.Furthermore, in this drawing the processing chamber 39 is connected totwo modules 11. The two modules 11 are each connected to a differentliquid supply so that multiple processes may be performed in theprocessing chamber 39.

In operation, the chemical vapor delivery system shown in FIG. 1 worksvery effectively with silylating agents, such as (hexamethyldisilazane)HMDS, (hexamethylcyclotrisilazane) HMCTS, (trimethylsilyldimethylamine)TMSDMA, (trimethylsilyldiethylamine) TMSDEA,(dimethylsilyldimethylamine) DMSDMA, (bis(dismethylsilyl)dimethylamine)B(DMS)DMA, and (bis(dimethylsilyl)methylamine) B(DMS)MA. The mass flowcontroller 11 heats the silylating agents to temperatures in the rangeof 25° to 200° C.

With the module 11 integrally mounted to the processing unit 10 and itsprocessing chamber 39, a feed line is eliminated. Condensation is not aproblem and the silylating agents can be delivered to the processingchamber 39 at precise temperatures and pressures. Among other benefits,the present invention avoids the complications resulting from therequirements of heating the feed line and maintaining it at a precisetemperature, or connecting individual components together and having toheat each component.

Furthermore, the agents are distributed uniformly upon the wafer in theprocessing chamber 39.

Besides silylating agents, the present invention can be used for otherliquid organosilanes and also other liquid sources used in etching anddiffusion. One example is (tetraethyloxysilane) TEOS which is used fordepositing silicate glass on a semiconductor wafer. TEOS vapor isdelivered to the processing chamber 39 and semiconductor wafer at a muchhigher rate than the vapors of silylating agents. For example, typicalflow rates for TEOS are 1 to 60 cc. per second, while silylating agentflow are 0.1 to 1 cc. per second. Hence the vapor flow rates in TEOSoperations become more critical.

For TEOS the module 11 is modified from operation as a pressurecontroller as described to a operation as a mass flow controller. Themodule 11 remains the same as described above with an added flow sensor65 between the proportioning pressure valve 21 and the fitting andoutlet 62, as shown symbolically in FIG. 8, to an gas supply inlet to aprocessing chamber. The control block 17 of FIG. 1 is modified. Asstated with respect to a previous embodiment, the microprocessor in theunit 17 controls the temperature of the module 11, the temperature ofthe manometer 19, and the refilling operation of the reservoir 44.However, rather than the feedback signals from the manometer 18, themicroprocessor also controls the flow of the vaporized TEOS with theproportioning pressure valve 21 in response to the feedback signals fromthe flow sensor 65.

However, as explained above, mass flow controllers (and their sensors)typically have difficulty operating at temperatures above 70 degrees C.In operation, the module 11 heats the reservoir 44 up to a maximumtemperature of 185° C. to get the liquid TEOS into a vapor state. Otheragents may require higher temperatures. For, a better way of operationas a mass flow controller in addition to the manometer 19, a secondmanometer may be connected between the valve 21 and the outlet 62. Withthe microprocessor in the control unit 17, the flow from the reservoir44 through the outlet 62 is calculated by the difference in pressurereadings from the two manometers. Based upon the calculated value, thevalve 21 is adjusted by a signal from the unit 17 to control the vaporflow.

FIG. 7 illustrates a modification of the module 11 for an extended rangeof mass flow control. In the modification three gas channels are formedbetween the heated reservoir in the module and the gas outlet to aprocessing chamber. In FIG. 7 a shut-off valve 72 and level sensor 73help control the level of the liquid in the reservoir in the modifiedmodule 81, as described previously. A capacitance manometer 79 measuresthe pressure at the reservoir. Connected to the reservoir are three gaschannels, each formed by a proportioning pressure valve, 70A-70C,between two shut-off valves 71A-71C and 72A-72C and their respectivefittings (not shown). The outlet of the fittings for the shut-off valves72A-72C are connected to a second manometer 78 and its fitting (notshown), which in turn is connected to an outlet fitting 83 with anoutlet 82 for a direct connection to an gas inlet to a processingchamber.

The shut-off valves 71A-71C and 72A-72C are operated to open one gaschannel at a time for operation. Each channel has two shut-off valves toisolate each inoperative channel so that any backflow of the vapor intothe channel is prevented.

The three gas channels permit three different flow ranges for themodified module. Typically a single channel under the control of theproportioning pressure valve can be operated so that the vapor flow canbe operated over a decade, i.e., the flow rate can be varied from a flowunit to, say, 20 flow units. With the three channels, each of theproportioning pressure valves 70A-70C can be calibrated so that vaporflow operation can be extended over three decades or more. As describedpreviously the two manometers provide the pressure differential to allowdetermination of flow rate of the selected channel. Note that themodified module need not be operated as a mass flow controller, but alsoa pressure controller with extended range of operation.

If the channels are operated at such disparate pressures that themanometers 78 and 79 cannot measure the pressures for all the operatingconditions, then the module 81 may be modified so that a pair ofmanometers is placed on either side of a proportioning valve 70A-70C ineach channel. The manometers are calibrated to operate under theconditions for each channel.

Another modification is the addition of a vent to a module operating asa mass flow controller. Located in the channel before the outlet isreached, a diverter valve controls the flow of vapor from the module'sheated reservoir either through the outlet into the processing chamberor through the vent. Without the vent, the vapor flows into processingchamber as soon as the chamber feed valve 21 is opened. Under theseinitial conditions the rate of mass flow may not desirable. The vent anddiverter valve permit the initial vapor flow rate through the vent to bestabilized and adjusted to the desired flow rate. Then the divertervalve is operated and the vapor flow shifted through the outlet of themodule and into the processing chamber.

With this flexibility of operating conditions, the present invention canbe used for many chemical processes having liquid sources. Carbontetrachloride in etching processes may be used in the present inventionand doping processes may be carried out by the present invention. Thepresent invention may even handle chemical sources which are initiallysolid. The solid source may be heated itself so that the chemical solidis liquified so the chemical liquid can be sent to the integrated moduleof the present invention.

While the above is a complete description of the preferred embodimentsof the invention, various alternatives, modifications and equivalentsmay be used. It should be evident that the present invention is equallyapplicable by making appropriate modifications to the embodimentsdescribed above. Therefore, the above description should not be taken aslimiting the scope of the invention which is defined by metes and boundsof the appended claims.

What is claimed is:
 1. An integrated chemical vapor delivery system fordelivery of chemical vapor from a liquid source to a processing unitwith a processing chamber therein for semiconductor wafers, said systemcomprisinga housing having a wall and means for mounting said housing tosaid processing chamber; a reservoir defined by said housing for holdinga liquid from said source, said reservoir connected to said source andto said processing chamber when said module housing is mounted to saidprocessing unit; means in said housing walls for heating said reservoirso that liquid in said reservoir is transformed into a vapor; and meansin said housing for controlling the delivery of said vapor from saidreservoir to said processing chamber; whereby said system controllablysupplies vapor from said liquid supply to said processing chamber. 2.The system as in claim 1 further comprisingmeans in said housing forsensing a property of said vapor in the delivery of said vapor from saidreservoir to said processing chamber.
 3. The system as in claim 2wherein said controlling means is coupled to said sensing means so thatthe delivery of said vapor to said processing chamber is controlled bysaid sensed property.
 4. The system as in claim 3 wherein saidcontrolling means comprises a first valve connected between saidreservoir and said processing chamber, said first valve regulating theflow of said vapor from said reservoir to said processing chamber. 5.The system as in claim 4 wherein said first valve comprises aproportioning valve.
 6. The system as in claim 3 wherein said sensingmeans comprises means for sensing the pressure in said processingchamber.
 7. The system as in claim 3 wherein said means comprises meansfor sensing the flow of said vapor from said reservoir to saidprocessing chamber.
 8. The system as in claim 7 wherein said flowsensing means comprises means for determining a pressure differentialbetween two locations along the flow of said vapor from said reservoirto said processing chamber for determining the flow rate of said vapor.9. The system as in claim 1 further comprising means in said housing forsensing the amount of said liquid in said reservoir.
 10. The system asin claim 9 wherein said amount sensing means determines the level ofsaid liquid in said reservoir.
 11. The system as in claim 9 furthercomprising a second valve in said housing, said valve connected betweensaid liquid supply and said reservoir and coupled to said sensing means,said valve responsive to said amount of liquid in said reservoir so thatliquid is maintained in said reservoir from said supply.
 12. The systemas in claim 1 further comprising a third valve in said housing, saidvalve connected between said reservoir and said processing chamber, saidvalve capable of shutting off said vapor from said reservoir to saidprocessing chamber.
 13. The system as in claim 1 wherein said reservoirheating means comprises resistance heating rods mounted in said housing.14. The system as in claim 1 wherein said liquid comprises a silylationagent.
 15. An integrated module for the delivery of chemical vapor froma liquid source through an inlet to a processing chamber of a processingunit for semiconductor wafers, said module comprisinga housing defininga reservoir for holding a liquid from said source; a supply channelconnecting said reservoir to a supply inlet for connection to saidsource; a gas channel connecting said reservoir to an outlet; means formounting said housing to said processing unit such that said outlet isconnected to said processing chamber inlet; means in said housing forheating said reservoir so that liquid in said reservoir is transformedinto vapor; and means in said housing connected to said gas channel forcontrolling the delivery of said vapor from said reservoir to saidprocessing chamber; means in said housing for sensing a property of saidvapor from said reservoir to said processing chamber; whereby saidmodule controllably supplies vapor from said liquid supply to saidprocessing chamber.
 16. The module as in claim 15 wherein saidcontrolling means is coupled to said sensing means so that the deliveryof said vapor to said processing chamber is controlled by said sensedproperty.
 17. The module as in claim 16 wherein said controlling meanscomprises a first valve connected to said gas channel for regulating theflow of said vapor from said reservoir to said processing chamber. 18.The module as in claim 17 wherein said third valve comprises aproportioning valve.
 19. The module as in claim 16 wherein said sensingmeans comprises means for sensing the pressure in said processingchamber.
 20. The module as in claim 16 wherein said means comprisesmeans for sensing the flow of said vapor through said gas channel. 21.The module as in claim 20 wherein said flow sensing means comprisesmeans for determining a pressure differential between two locations insaid gas channel for determining the flow rate of said vapor.
 22. Themodule as in claim 15 further comprising means in said housing forsensing the amount of said liquid in said reservoir.
 23. The module asin claim 22 wherein said amount sensing means determines the level ofsaid liquid in said reservoir.
 24. The module as in claim 22 furthercomprising a second valve in said housing, said valve connected to saidsupply channel, said valve responsive to said amount of liquid in saidreservoir so that liquid is maintained in said reservoir from saidsupply.
 25. The module as in claim 15 further comprising a third valvein said housing, said valve connected to gas channel, said valve capableof shutting off said vapor from said reservoir to said processingchamber.
 26. The module as in claim 15 wherein said reservoir heatingmeans heats said housing to heat said reservoir.
 27. The module as inclaim 15 comprising a vent and a diverter valve connected to said gaschannel, said diverter valve selectably sending said vapor through saidvent or through said outlet.
 28. The module as in claim 26 wherein saidhousing has walls and said reservoir heating means comprises; resistanceheating rods mounted in said housing walls.
 29. The module as in claim15 wherein said liquid comprises a silylation agent.
 30. An integratedmodule for the delivery of chemical vapor from a liquid source throughan inlet to a processing chamber of a processing unit for semiconductorwafers, said module comprisinga metal housing having solid lower andupper parts, said lower and upper parts fitting together, said lowerpart having walls defining a reservoir for holding a liquid from saidsource; a supply channel in said upper housing part connecting saidreservoir to a supply inlet for connection to said source; a gas channelin said upper housing part connecting said reservoir to an outlet; meansfor mounting said housing to said processing unit such that said outletis connected to said processing chamber inlet; means in said walls ofsaid upper housing part for heating said reservoir so that liquid insaid reservoir is transformed into vapor; and means integrally mountedto said housing and connected to said gas channel for controlling thedelivery of said vapor from said reservoir to said processing chamber;whereby said module controllably supplies vapor from said liquid supplyto said processing chamber.
 31. The system as in claim 30 wherein saidliquid comprises a silylation agent.
 32. The module as in claim 30further comprisingmeans integrally mounted in said upper housing partfor sensing a property of said vapor in the delivery of said vapor fromsaid reservoir to said processing chamber; and wherein said controllingmeans is coupled to said sensing means so that the delivery of saidvapor to said processing chamber is controlled by said sensed property,said controlling means comprising a proportioning valve connected tosaid gas channel for regulating the flow of said vapor from saidreservoir to said processing chamber.
 33. The module as in claim 30further comprisingmeans integrally mounted in said lower housing partfor sensing the amount of said liquid in said reservoir to determine thelevel of said liquid in said reservoir; and a valve integrally mountedin said lower housing part connected to said supply channel, said valveresponsive to said amount of liquid in said reservoir so that liquid ismaintained in said reservoir from said supply.
 34. The module as inclaim 30 further comprising a valve integrally mounted in said upperhousing part, said valve connected to said gas channel, said valvecapable of shutting off said vapor from said reservoir to saidprocessing chamber.